Paper sheets and sheets of paper laminated with metallic foil are used in a variety of wrapping and packaging applications. Consumer items, such as confectionery, are often wrapped individually or in bundles in such paper or foil sheets, and cigarettes and cigars are often sold in tins or boxes lined with such foil sheets. Laminated metallic foil sheets are particularly useful as package liners for tobacco products because the metal foil forms a barrier to light and moisture which could degrade the tobacco.
Laminated metallic foil sheets and paper sheets used as wrappers or packaging liners are often embossed to show images such as patterns, trade marks, company names, logos, or other information in order to enhance the presentation of goods wrapped or packaged with such sheets. The embossing may be carried out by well-known processes such as roll to roll embossing, in which a strip of laminated foil or paper is fed and pressed between a pair of embossing rollers.
For example, it is well known in the tobacco industry to use an embossing technology based on passing a laminated metallic foil through a press having two hardened steel embossing rollers, one being a drive roller and the other being driven by the drive roller. In one technique, the embossing rollers are each initially machined with mating die patterns consisting of an array of small pyramidal projections that extend over the entire roller surface. The pyramidal projections act as embossing dies to produce a pattern as the sheet passes between the rollers. In order to create images appearing on the embossed sheet, the pyramidal projections of the drive roller are partly or completely removed in areas that reflect the shape of the image to be depicted. Once embossed, the metallic foil sheet bears the pattern of the pyramidal die array everywhere except for the areas corresponding to the images. The images are thus produced by leaving part of the sheet unembossed while the embossed pattern provides a background for the images. In the present specification, therefore, it will be understood that the term “embossed image” includes an image created by embossing a background pattern that surrounds an unembossed image area.
The embossing rollers used for this type of embossing technique are normally dedicated to a single product line for which the rollers can produce an embossed strip of laminated foil or paper which is then cut into uniform sheets. All of the sheets so produced look exactly the same, bearing the same embossed background pattern and images. Consequently, when a product is to be packaged with sheets bearing different images, for example sheets having written matter in different languages, it is necessary to use different sets of embossing rollers. Each time embossed sheets having different appearances are to be produced, one set of embossing rollers must be switched in the press for another set of embossing rollers. Alternatively, other production lines must be set up with additional embossing presses having different sets of embossing rollers. This is a disadvantage because additional manufacturing costs must be incurred to produce embossed sheets with different images. In the first case, the cost is due to lost production caused by production down time while the embossing rolls are changed. In the second case, the cost is for additional presses and other equipment.
There is therefore a need for an embossing technique that provides added flexibility in the production of different images or embossing patterns on sheets of paper or laminated metal foil.